(#1998) - fix intermittent safari replication error

In Safari 6 I am occasionally (about 1/10 times) seeing an error in this test, because sometimes Safari is sending the `cancel` XHR to `_replicate` after sending the `PUT`, even though in the code it looks like the `PUT` should go first.  I have screenshot evidence below to prove that this Sasquatch exists.

Since there doesn't seem to be any way to have the `promise.cancel` in `replicate.js` communicate with the `changes` object in `changes.js` (nor should there be, probably), tweaking the test seems like the best solution.

![screenshot 2014-04-20 21 02 13](https://cloud.githubusercontent.com/assets/283842/2752417/f3f31cac-c90a-11e3-8189-5229d63fdd07.png)